Dan Rooney, the longtime Pittsburgh Steelers chairman who led the NFL’s diversity efforts for decades, has died, the team announced Thursday.

He was 84.

Rooney’s first job with the Steelers, a team his family has controlled since 1933, was as a water boy at age 12 and he began working in the front office after he graduated from Duquesne University in 1955. He eventually served as general manager and ran the day-to-day operations of the club from 1975 through 2003 when Dan Rooney’s son, Art Rooney Jr., took over those duties.

The Rooneys and the Maras, who have controlled the New York Giants since 1925, are considered the first families of the NFL, though it wasn’t until the NFL-AFL merger announced in 1966 that the Steelers became a powerhouse.

The Steelers shifted to the American Football Conference in 1970, the same season the franchise began play at Three Rivers Stadium, and Pittsburgh became the most dominant team of the decade led by the likes of Terry Bradshaw, Jack Lambert, Franco Harris and head coach Chuck Noll. The team won six consecutive AFC Central titles to close out the decade, a run that included four Super Bowl titles. .

Tributes began across social media and other places soon after Rooney's death was announced.

"Dan Rooney was a great friend of mine, but more importantly, he was a great friend to the people of Pittsburgh, a model citizen, and someone who represented the United States with dignity and grace on the world stage," said President Obama in a statement. "I knew hed do a wonderful job when I named him as our United States Ambassador to Ireland, but naturally, he surpassed my highest expectations, and I know the people of Ireland think fondly of him today. And I know the people of Pittsburgh, who loved him not only for the Super Bowl championships he brought as the owner of the Steelers, but for his generosity of spirit, mourn his passing today. Michelle and I offer our condolences to the Rooney family, some of the most gracious and thoughtful people we know - even as we celebrate the life of Dan Rooney: a championship-caliber good man."

"Few men have contributed as much to the National Football League as Dan Rooney," NFL Commissioner Roger Goodell wrote in a statement. "A member of the Pro Football Hall of Fame, he was one of the finest men in the history of our game and it was a privilege to work alongside him for so many years. Dan’s dedication to the game, to the players and coaches, to his beloved Pittsburgh, and to Steelers fans everywhere was unparalleled. He was a role model and trusted colleague to commissioners since Bert Bell, countless NFL owners, and so many others in and out of the NFL. A voice of reason on a wide range of topics, including diversity and labor relations, Dan always had the league’s best interests at heart. For my part, Dan’s friendship and counsel were both inspiring and irreplaceable. My heart goes out to Patricia, Art, and the entire Rooney family on the loss of this extraordinary man."

Pro Football Hall of Fame president and CEO David Baker said the organization would fly the flag at half-staff on Friday in honor of Rooney.

“The Pro Football of Fame family mourns the loss of an incredible and loving man," Baker said in a statement. "Ambassador Rooney epitomized all that is GREAT about this game that he and his family helped grow into an American institution. His impact on the game was profound.

Former coach Bill Cowher said in a tweet: "RIP Dan. My Mentor & friend. Thank you for your Guidance & Wisdom. I came a Young Coach & left a Better Man. Your spirit will live forever."

Steelers wide receiver Antonio Brown left a heartfelt message on Instagram that said, in part, "You looked at me as more than just another jersey number. One of the most genuine, and humble human beings I've had the pleasure of knowing. You motivated me not only to excel on the field but also in life. This season, the number 84 on my uniform will represent the 84 years you spent on this earth making an impact on the lives of others."

In his later years, Rooney became powerful in league circles on many levels, and is best known for the league’s effort to make the league’s coaching ranks more diverse and his appointment as ambassador of Ireland by President Obama.

This is how Cowher described him, according to the Pittsburgh Post-Gazette: “He was like a father, a friend, a mentor, a boss who inspired others around him. He was a people person and he never forgot where he came from. He epitomized Pittsburgh — hard working, humble, no-nonsense, tell it the way it is and never forget where he came from. That’s him, that’s Pittsburgh.”

The Rooney Rule, created in 2003, required teams to interview minorities for head coaching vacancies and senior football operations jobs. The rule was expanded in 2016 to include women for executive openings.

"In the past, we've had some that were just token interviews," Rooney told USA TODAY Sports in May 2013. "They talked to someone on their staff for two minutes and said, 'Ok.' This hasn't been happening now. So I don't think you can get all excited over (backlash from) one year."

Seventeen minority head coaches were hired from 2003 through 2017, more than double the number that had been hired since the NFL’s founding in 1920.

There are currently eight minority coaches in the NFL, including Steelers coach Mike Tomlin.

Rooney, a supporter of President Obama’s 2008 presidential campaign, was appointed as the ambassador to Ireland in 2009 and held the post until 2012. Rooney had long been a supporter of Ireland, raising millions to support cultural and education efforts in the country.

Rooney’s father, Art Rooney Sr., purchased the Steelers in 1933, a year after Dan Rooney’s birth with, urban legend has it, $2,500 in racetrack winnings. The Rooney family has long had business interests in horse and dog tracks, which led the Steelers to change its ownership structure to comply with NFL anti-gambling rules.